1. Field of the Invention
The invention relates to a private branch exchange which can be connected to a network for providing a transmission partner's number notification service.
2. Related Background Art
At present, in the INS (Information Network System) as an ISDN of Japan, a transmission partner's number notification service to notify the transmission user's number (including the sub address) to the reception user is executed. In the above service between the terminals, the transmission user can select whether the transmission partner's number is notified every call or not. Generally, when the transmission partner's number can be notified, the transmission user's number (transmission partner's number) is sent every call upon transmission. When the transmission partner's number is not notified by the transmission user, the INS adds the transmission partner's number of the default at the time of the contraction and sends to the reception terminal in accordance with the content of the contract (for instance, when the notifying mode is an always permitting mode).
The transmission partner or the like can be discriminated on the reception side by the above service. Various kinds of services such as a check and the like of a membership system of a data base, a telemarketing, or the like have been realized.
In the private network such as a PBX or the like, hitherto, in the case where a call is generated from an extension terminal by using the INS, the INS adds a pilot number (representative number) and sends to the reception terminal so long as the private network has already made a representative contract. As described in "An Exchange Terminology" (An Electronics and Communication Terminology No. 15) published in Japan by the Institute of Electronics and Communication Engineers of Japan (IECE) on Mar. 31, 1983, "pilot number service" refers to a service in which call reception to plural telephone sets is performed by using a single telephone number. The plural telephone sets are grouped, and one of these telephone sets is selected as the representative telephone set. When a call to a representative subscriber is received, the call is connected to the free (i.e., not busy) telephone set in the group according to a predetermined priority order. When the representative contract is not made yet, the INS adds the number of the default upon contract of the line which is connected as a transmission partner number and sends to the reception terminal.